Near-field wireless power transmission techniques for a wireless-power receiver

ABSTRACT

A wireless-power receiver is disclosed including a first antenna configured to transmit first near-field radio frequency (RF) energy, a second antenna configured to receive second near-field RF energy, and a communications component configured to provide a communication signal including data indicating a location of the first wireless-power receiver. The wireless-power receiver is configured to, in accordance with a determination that the wireless-power receiver is in direct contact with a surface of another wireless-power receiver, transmit the first near-field RF energy, via the first antenna, to the other receiver. The wireless-power receiver is further configured to, in accordance with a determination, based on the data indicating the location of the wireless-power receiver, that the wireless-power receiver is within a non-zero threshold distance from the other receiver or a wireless-power transmitter, receive the second near-field RF energy, via the second antenna, from the other receiver or from the wireless-power transmitter.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. Non-Provisional patent application Ser. No. 16/051,336, entitled “Unit Cell Of A Wireless Power Transmitter For Wireless Power Charging,” filed Jul. 31, 2018 which is a continuation of U.S. Non-Provisional patent application Ser. No. 15/047,831, entitled “Systems and Methods of Wireless Power Charging Through Multiple Receiver Devices, filed Feb. 19, 2016, (now U.S. Pat. No. 10,038,332), which claims the benefit of U.S. Provisional Patent Application Ser. No. 62/271,837, entitled “Systems and Methods of Wireless Power Charging through Multiple Receiving Devices,” filed Dec. 28, 2015, and U.S. Provisional Patent Application Ser. No. 62/387,465, entitled “Systems and Methods of Wireless Power Charging through Multiple Receiving Devices,” filed Dec. 24, 2015, each of which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

Generally, the present disclosure relates to wireless charging. More particularly, the present disclosure relates to low-power near field charging surfaces.

BACKGROUND

Electronic devices, such as laptop computers, smartphones, portable gaming devices, tablets, or others, require power to operate. As generally understood, electronic equipment is often charged at least once a day, or in high-use or power-hungry electronic devices, more than once a day. Such activity may be tedious and may present a burden to some users. For example, a user may be required to carry chargers in case his electronic equipment is lacking power. In addition, some users have to find available power sources to connect to, which is time consuming. Lastly, some users must plug into a wall or some other power supply to be able to charge their electronic device. However, such activity may render electronic devices inoperable or not portable during charging.

Some conventional solutions include an inductive charging pad, which may employ magnetic induction or resonating coils. As understood in the art, such a solution still requires the electronic devices to: (i) be placed in a specific location on the inductive charging pad, and (ii) be particularly oriented for powering due to electromagnetic fields having a particular orientation. Furthermore, inductive charging units require large coils in both devices (i.e., the charger and the device being charged by the charger), which may not desirable due to size and cost, for example. Therefore, electronic devices may not sufficiently charge or may not receive a charge if not oriented properly on the inductive charging pad. And, users can be frustrated when an electronic device is not charged as expected after using a charging mat, thereby destroying the credibility of the charging mat.

Other conventional solutions use far field RF wave transmission to create pockets of energy at remote locations for charging a device. Such solutions, however, are better suited for particular uses and configurations as far field RF wave transmission solutions typically use numerous antenna arrays and circuitry for providing phase and amplitude control of the RF waves. Accordingly, there is a desire for an economical application of a charging surface that allows for low-power, wireless charging without requiring a particular orientation for providing a sufficient charge.

SUMMARY

In one embodiment, the present disclosure provides a method for charging an electronic device, the method comprising applying an RF signal to a charging surface having a plurality of unit cells to cause an RF energy signal to be present within the unit cells of the charging surface for charging the electronic device in response to an antenna of the electronic device being positioned in a near-field distance from at least one of the unit cells. The unit cells may at least in part be a periodic structure, where the periodic structure may be locally periodic while being adaptive as function of location within the structure.

In one embodiment, the present disclosure provides a charging surface device comprising: circuitry configured to generate an RF signal; and a plurality of unit cells configured to receive the RF signal and cause an RF energy signal to be present for charging an electronic device in response to an antenna of the electronic device being positioned in a near-field distance measured from a surface of at least one of the unit cells.

In one embodiment, the present disclosure provides a method for charging an electronic device, the method comprising: applying an RF signal to a plurality of unit cells of a charging surface to cause an RF energy signal to be present within the unit cells of the charging surface; receiving the RF energy signal at an antenna of a wireless device when the antenna is positioned in a near-field distance from at least one of the unit cells; and charging a battery of the electronic device in response to the antenna receiving the RF energy signal.

In one embodiment, the present disclosure provides a system comprising: RF circuitry configured to generate an RF signal; an adaptive coupling surface (here, a charging surface) comprising a plurality of unit cells configured to receive the RF signal and to cause an RF energy signal to be trapped/stored within the unit cells when the receiver device is not present and to leak the energy when the receiver is within a near-field region of the surface. Receiver circuitry of an electronic device to be charged may be configured to charge the electronic device in response to an antenna of the electronic device receiving the RF energy signal when the antenna is positioned in a near-field distance from one or more of the unit cells (of the coupling surface).

In one embodiment, the present disclosure provides a method for charging an electronic device, the method comprising: generating an RF signal; applying the RF signal, by a conductive line extending through a via, to a patch antenna member of a unit cell (i.e., located within the coupling surface, where the patent antenna member or exciting element may be a part of the coupling surface design (e.g., one of the unit cells) or the exciting element may be an additional element placed within the other unit cells); generating, by the patch antenna, an RF energy signal in the unit cell; and leaking the RF energy signal from the unit cell to an antenna of the electronic device when the antenna is positioned in a near-field distance from the unit cell.

In one embodiment, the present disclosure provides a charging surface device comprising: a plurality of unit cells configured to receive one or more RF signals, each unit cell including: a patch antenna configured to: (i) receive one of the one or more RF signals, and (ii) generate an RF energy signal for charging an electronic device, and an aperture configured to leak the RF energy signal from the unit cell when an antenna of the electronic device is positioned in a near-field distance from the unit cell.

In one embodiment, the present disclosure provides a method for charging a device, the method comprising: applying an RF signal to a plurality of unit cells of a charging surface to cause an RF energy signal to be present within the unit cells of the charging surface; and filtering the RF energy signal using a harmonic screen filter element to produce the RF energy signal for charging the electronic device in response to an antenna of the electronic device being positioned in a near-field distance from at least one of the unit cells.

In one embodiment, the present disclosure provides a charging surface device comprising: circuitry configured to generate an RF signal; a plurality of unit cells configured to receive the RF signal and to cause an RF energy signal to be present within one or more of the unit cells; and a harmonic screen filter element configured to filter the RF energy signal for charging the electronic device in response to an antenna of the electronic device being positioned in a near-field distance from at least one of the unit cells.

In one embodiment, the present disclosure provides a method of manufacturing a charging surface device, the method comprising: coupling circuitry configured to generate an RF signal to a plurality of unit cells, the plurality of unit cells configured to receive the RF signal and to cause an RF energy signal to be present within one or more of the unit cells; and attaching a harmonic screen filter element configured to filter the RF energy signal for charging the electronic device in response to an antenna of the electronic device being positioned in a near-field distance from at least one of the unit cells.

In one embodiment, the present disclosure provides a method for charging an electronic device, the method comprising: receiving, by an antenna configured with a bandwidth that includes a center frequency and used to communicate wireless signals, a wireless charging signal operating at the center frequency, the wireless charging signal received from a charging surface positioned in a near-field distance from the antenna; and responsive to determining that the antenna is receiving a power above a threshold level, routing the received wireless charging signal to a rectifier to convert the wireless charging signal to a power signal.

In one embodiment, the present disclosure provides a system comprising: receiver circuitry configured to determine a power from a wireless charging signal received by an antenna used to communicate wireless signals, the wireless charging signal received by the antenna from a charging surface positioned in a near-field distance from the antenna; comparator circuitry configured to compare the power to a threshold level; rectifier circuitry configured to rectify the received wireless charging signal to produce a rectified signal; a voltage converter configured to convert the rectified signal to a voltage to charge a chargeable battery; and switching circuitry configured to route the received wireless charging signal to the rectifier when the power exceeds the threshold level.

In one embodiment, the present disclosure provides a method for charging an electronic device, the method comprising: receiving a signal indicative of a request for charging the electronic device; generating, in response to receiving the signal, an RF signal; applying the RF signal to a plurality of unit cells of a charging surface to cause an RF energy signal to be present in the unit cells of the charging surface for charging the electronic device; and leaking the RF energy signal from the unit cells of the charging surface to an antenna of the electronic device when the antenna is positioned in a near-field distance to at least one of the unit cells.

In one embodiment, the present disclosure provides a charging surface device comprising: control circuitry configured to receive a signal indicative of a request for charging an electronic device; a plurality of patch antennas each configured to generate an RF energy signal; and a plurality of unit cells configured to leak the RF energy signal from the unit cells when an antenna of the electronic device is tuned to the center frequency and positioned in a near-field distance from at least one of the unit cells.

In one embodiment, the present disclosure provides a method for charging an electronic device, the method comprising: producing a low-power RF energy signal in a unit cell of a charging surface; leaking the low-power RF energy signal from the unit cell of the charging surface to an antenna of the electronic device when the antenna is positioned in a near-field distance from the unit cell; sensing the low-power RF energy signal in the unit cell of the charging surface; comparing the low-power RF energy signal in the unit cell of the charging surface to a threshold level; and producing, if the low-power RF energy signal is below the threshold level, a subsequent low-power RF energy signal in the unit cell of the charging surface.

In one embodiment, the present disclosure provides a charging surface device comprising: a feeding element, such as a patch antenna, may be configured to produce a low-power RF energy signal; a unit cell inclusive of the feeding element, here the patch antenna, the unit cell configured to retain the low-power RF energy signal when an antenna of an electronic device is not positioned in a near-field distance from the unit cell, and configured to leak the low-power RF energy signal when the antenna of the electronic device is positioned in the near-field distance from the unit cell; and control circuitry configured to sense the low-power RF energy signal in the unit cell, compare the low-power RF energy signal to a threshold, and to cause, if the low-power RF energy signal is below the threshold, the patch antenna to produce a subsequent low-power RF energy signal stored in the unit cell.

In one embodiment, the present disclosure provides a method for charging an electronic device, the method comprising: leaking an RF energy signal from a charging surface in response to a metal structure being proximately positioned at a surface of the charging surface to cause the RF energy signal to enter a space formed between the surface of the charging surface and the metal structure so that an antenna of the electronic device can receive the leaked RF energy signal and route the received RF energy signal to a rectifier to convert the RF energy signal to charge a chargeable battery.

In one embodiment, the present disclosure provides a method for charging an electronic device, the method comprising: applying an RF signal to a plurality of unit cells of a charging surface to cause an RF energy signal to be present within the unit cells of the charging surface; and leaking the RF energy signal from one or more of the unit cells to a gap formed between a surface of the charging surface and a metal portion of the electronic device positioned in a near-field distance from the one or more of the unit cells to cause an antenna of the electronic device to receive the RF energy signal for charging the electronic device.

In one embodiment, the present disclosure provides a charging surface device comprising: circuitry configured to generate an RF signal; and a plurality of unit cells configured to receive the RF signal and to cause an RF energy signal to be present in the unit cells for charging an electronic device positioned in a near-field distance from one or more of the unit cells by leaking the RF energy signal from the one or more of the unit cells to a cavity/gap formed between a surface of the charging surface and a metal portion of the electronic device to cause an antenna of the electronic device to receive the RF energy signal for charging the electronic device.

In an embodiment, a system for wireless power transfer comprises a first device comprising a first antenna configured to receive one or more RF signals from a charging surface, and a second antenna configured to transmit and receive one or more RF signals to one or more devices in a proximity to the first device; and a second device comprising a first antenna configured to receive the one or more RF signals from the first device, and a battery configured to be charged in response to the second device receiving the one or more RF signals from the first device when the second device is within the proximity to the first device.

In an embodiment, a method for wireless power transfer comprises transmitting, by an antenna of the first device, one or more RF signals to a second device in a proximity to the first device, wherein the second device comprises a first antenna configured to receive the one or more RF signals from the first device, and a battery configured to be charged in response to the second device receiving the one or more RF signals from the first device when the second device is within the proximity to the first device.

In an embodiment, a wireless device comprises a first antenna configured to receive one or more RF signals from a charging surface, and a second antenna configured to transmit and receive one or more different RF signals to one or more wireless devices in a proximity to the wireless device. The wireless device is configured to convert the RF energy into electrical energy for charging a battery.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure are described by way of example with reference to the accompanying figures, which are schematic and may not be drawn to scale. Unless indicated as representing prior art, the figures represent aspects of the present disclosure.

FIG. 1A is an illustration of an example embodiment of an electronic device positioned on an illustrative charging surface that produces an RF energy signal for charging the electronic device, in accordance with an embodiment of the present disclosure;

FIG. 1B is an illustration of an illustrative table inclusive of a surface on which an electronic device is positioned, in accordance with an embodiment of the present disclosure;

FIG. 2A is a schematic diagram of an illustrative charging surface for generating RF energy signals to charge an electronic device, in accordance with an embodiment the present disclosure;

FIG. 2B is a flow diagram illustrating operation of the illustrative charging surface in accordance with one or more embodiments of the present disclosure;

FIG. 2C is a flow diagram illustrating a more detailed operation of the illustrative charging surface in accordance with one or more embodiments of the present disclosure;

FIG. 3A is a schematic diagram of an illustrative electronic device for receiving the RF energy signals generated by a charging surface, in accordance with an embodiment of the present disclosure;

FIG. 3B is a flow diagram illustrating operation of the illustrative electronic device in accordance with one or more embodiments of the present disclosure;

FIG. 4A is an illustrative schematic diagram of circuitry representing the charging surface when no electronic device is positioned within the near-field distance;

FIG. 4B is an illustrative schematic diagram of circuitry representing the charging surface when an electronic device is positioned within the near-field distance;

FIG. 4C shows schematic models of equivalent circuits with two states of energy flow without and with an electronic device positioned in a near-field distance of the charging surface;

FIG. 4D is an illustration of an alternative representation of the schematic models of FIG. 4C;

FIG. 5A is an illustration of a top-side view of an example embodiment of an antenna portion of a charging surface including two substrate layers, in accordance with an embodiment of the present disclosure;

FIG. 5B is a bottom-side view of an example embodiment of the feeding portion (i.e. slot being made into the ground plane of the surface) of a charging surface including two substrate layers, in accordance with an embodiment of the present disclosure;

FIG. 5C is a perspective view of an example embodiment of a unit cell used for the antenna portion of the charging surface illustrated in FIGS. 5A and 5B, in accordance with an embodiment of the present disclosure;

FIG. 5D is an overhead view of the example embodiment of the unit cell illustrated in FIG. 5C, in accordance with an embodiment of the present disclosure;

FIG. 6A is a top-side view of an example embodiment of an antenna portion of a charging surface formed with one substrate layer, in accordance with an embodiment of the present disclosure;

FIG. 6B illustrates a bottom-side view of an example embodiment of an antenna portion of a charging surface formed with one substrate layer, in accordance with an embodiment of the present disclosure;

FIG. 6C illustrates a perspective view of an example embodiment of a unit cell including a portion of the antenna portion of the charging surface illustrated in FIGS. 6A and 6B, in accordance with an embodiment of the present disclosure;

FIG. 6D illustrates an overhead view of the example embodiment of the unit cell illustrated in FIG. 6C, in accordance with an embodiment of the present disclosure;

FIG. 6E is an illustration of a cross-sectional view of an illustrative charging surface inclusive of a plurality of unit cells;

FIG. 7A illustrates a cross-sectional view of an example embodiment of an electronic device positioned within a near-field distance from a charging surface, in accordance with an embodiment of the present disclosure;

FIG. 7B illustrates an illustrative electronic schematic of the electronic device of FIG. 7A;

FIG. 8A illustrates resonance of an example RF energy signal located between an electronic device with metallic surface and a surface of a charging device, in accordance with an embodiment of the present disclosure;

FIGS. 8B-8D illustrate a more detailed schematic of a charging surface that provides for a resonant-coupler to charge an electronic device, in accordance with an embodiment of the present disclosure;

FIG. 9 illustrates a flow diagram of an example method for charging an electronic device using a charging surface, where the electronic device communicates a signal indicative of a request to charge or otherwise pairs with the charging surface, in accordance with an embodiment of the present disclosure;

FIG. 10 illustrates a flow diagram of an example method for charging an electronic device using a charging surface when the electronic device does not communicate a signal indicative of a request to charge, in accordance with an embodiment of the present disclosure;

FIG. 11A illustrates a perspective view of an embodiment of a unit cell of a charging surface having a harmonic screen filter element, where the harmonic screen filter element is positioned on or above a top surface of the unit cell;

FIG. 11B illustrates a cross-sectional view of an embodiment of a unit cell of a charging surface having a harmonic screen filter element (note, the harmonic filter screen may also be made of periodic unit cells), where the harmonic screen filter element is positioned on or above a top surface of the unit cell;

FIG. 12A illustrates a perspective view of an embodiment of a unit cell of a charging surface having a harmonic screen filter element, where the harmonic screen filter element is positioned within a substrate layer of the unit cell; and

FIG. 12B illustrates a cross-sectional view of an embodiment of a unit cell of a charging surface having a harmonic screen filter element, where the harmonic screen filter element is positioned within a substrate layer of the unit cell.

FIG. 13A is a schematic diagram illustrating wireless power transfer among a plurality of devices, in accordance with an embodiment the present disclosure.

FIG. 13B is a schematic diagram illustrating wireless power transfer among a plurality of devices, in accordance with an embodiment the present disclosure.

FIG. 14A is a schematic diagram illustrating wireless power transfer among a plurality of devices, in accordance with an embodiment the present disclosure.

FIG. 14B is a schematic diagram illustrating wireless power transfer among a plurality of devices, in accordance with an embodiment the present disclosure.

FIG. 15 is a schematic diagram illustrating wireless power transfer among a plurality of devices, in accordance with an embodiment the present disclosure.

FIG. 16 is a flow diagram illustrating operations of the wireless power transfer among a plurality of devices, in accordance with an embodiment the present disclosure.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, which may not be to scale or to proportion, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings and claims are not meant to be limiting. Other embodiments may be used and/or and other changes may be made without departing from the spirit or scope of the present disclosure.

Wireless Charging & High-Impedance Surfaces

FIG. 1A illustrates an embodiment of the present disclosure related to a charging surface, where an exemplary electronic device 104 is positioned on an illustrative charging surface 102 that produces a radio frequency (RF) energy signal for charging the electronic device 104. The charging surface 102 is shown as a pad, but it should be understood that the charging surface 102 may have any configuration, such as a desktop surface or portion thereof, housing of another electronic or non-electronic device, or any other surface in which RF charging via near-field RF signals may be provided to charge or power an electronic device, as described herein. The charging surface 102 may generate one or more RF energy signals for wireless power transmission that are received by the electronic device 104 when the electronic device 104, and more specifically, an antenna of the electronic device 104, is positioned within a near-field distance (e.g., preferably less than approximately 4 mm) from the charging surface 102. Alternative near-field distances, both higher than 4 mm and lower than 4 mm depending on the application and configuration of the charging surface 102, may be utilized. The received RF energy signals are then converted to a power signal by a power conversion circuit (e.g., rectifier circuit) (not shown) for charging a battery of the electronic device 104. In some embodiments, the total power output by the charging surface 102 is less than or equal to 1 Watt to conform to Federal Communications Commission (FCC) regulations part 15 (low-power, non-licensed transmitters).

In some embodiments, the electronic device 104 may include any electronic device including the RF power converter components described herein. For example, the electronic device may be any of a variety of portable technologies, such as a tablet, laptop, cell phone, PDA, wearable device, such as smart watches, fitness devices, headsets, or any other portable, mobile, or other electronic device technology that is capable of being recharged or operated utilizing the principles described herein.

In some embodiments, a charging surface 102 may include a housing defined by a plurality of sidewalls 106, a top surface 108, and a bottom surface (not shown). The top surface 108 extends over the bottom surface. The sidewalls 106 span between the top surface 108 and the bottom surface. In some embodiments, the housing is formed of plastic, but alternatively or additionally can be formed of other material(s), such as wood, metal, rubber, glass, or other material that is capable of providing for the functionality described herein. As illustrated in FIG. 1A, the charging surface 102 has a shape of a cuboid, but other two-dimensional or three-dimensional shapes are possible, such as a cube, a sphere, a hemisphere, a dome, a cone, a pyramid, or any other polygonal or non-polygonal shape, whether having an open-shape or a closed-shape. In some embodiments, the housing is waterproof or water-resistant. The charging surface 102 may be stiff or flexible and optionally include a non-skid bottom surface to resist movement when placed on a desktop or tabletop. Similarly, the top surface 108 may be or include non-skid region(s) (e.g., strips) (not shown) or be entirely non-skid to resist motion between the surface 108 and an electronic device. Still yet, a bracket or other guide may be mounted to the top surface 108 to assist a user with positioning of an electronic device. The housing may contain various components of the charging surface 102, which are described in greater detail herein. Note, the charging surface may be made of heat-conductive material (e.g., aluminum nitride) to absorb heat from the receiver device. Moreover, the entire coupling surface may be made of high-DK (i.e., with high dielectric permittivity) plastics/ceramics that may also be used to mold the unit cells to form the surface.

As described in greater detail below, the charging surface 102 may include a plurality of unit cell antennas formed, at least partially, from a substrate material. The substrate may include a metamaterial (i.e., an artificial material being made using small, compared to a wavelength of a signal being transmitted, elements such as patches, dipoles or slots), such as FR4, Rogers, ceramic, or any other material known in the art. The unit cells are designed to retain the RF energy signal used to charge the electronic device 104 prior to the electronic device 104 being placed on the charging surface 102. That is, when there is no antenna of the electronic device 104 positioned within the near-field distance, or an antenna of the electronic device 104 is not tuned or otherwise configured to receive the RF energy signal, the unit cells do not leak or have minimal leakage of the RF energy signal. However, the unit cells are adaptably configured to allow the RF energy signal to leak from the unit cells to an antenna of the electronic device 104 when the receive antenna is positioned within the near-field distance from the unit cell, and is tuned to the frequency of the RF energy signal (or is otherwise configured to receive the RF energy signal). In the present disclosure, one embodiment of an antenna is considered “tuned” to a particular frequency when leakage of an RF energy signal from the charging surface 102 with metamaterial occurs. One or more surfaces of the unit cell may be formed using metamaterial. For example, a ground plane, antenna patch, and/or both may be formed of metamaterial depending on design criteria.

In configuring the unit cells of the charging surface 102, the unit cells may be periodically spaced and sized such that a frequency signal that is generated and propagating within a substrate of the unit cells may be substantially retained within the charging surface 102 prior to the electronic device 104 being placed within the near-field of the charging surface 102. That is, when an antenna of the electronic device 104 is place in the near-field of the charging surface 102, a change in the boundary conditions of the charging surface results due to capacitance and inductance electrical characteristics being introduced by the electronic device at the surface of the unit cells (see FIGS. 4A and 4B).

The surface may be designed so that electromagnetic tuning results to enable leakage at the particular unit cell(s) that are within the near-field distance of the antenna(s) of the charging surface 102. When “tuned” properly, an RF energy signal is retained within a substrate of the unit cells of the charging surface 102 and no or minimal leakage occurs. The RF energy signal, when no antenna is in the near-field of the charging surface 102, reflects from the surface of the charging surface 102, such that no or minimal leakage occurs. And, when “tuned” properly, as when an antenna of the electronic device 104 is within the near-field of the charging surface 102, the surface characteristics of the charging surface 102 change and the signals may become aligned with slot dipoles or other feature of the unit cell(s) at the location of the antenna of the electronic device 104 to cause leakage to occur at that location. In the event that a different frequency is to be used, a dimensional change may be made to the unit cells of the charging surface 102 to accommodate the different frequency to avoid leakage. As an example, if higher frequencies are used, smaller unit cells need to be included to provide similar performance.

With regard to FIG. 1B, an illustration of an illustrative table 110 inclusive of a surface 112 on which an electronic device 114 is positioned is shown. The surface 112 may fully or partially be configured to operate as a charging surface utilizing the same or similar principles and configuration as the charging surface 102. By providing a piece of furniture, for example, inclusive of a charging surface, the electronic device 114 may be placed on the charging surface 112 and the electronic device 114 will charge independent of a separate charging device or external pad, such as shown in FIG. 1A. It should be understood that a wide variety of devices, furniture, and/or structures may be configured to include a charging surface on one or more surface regions of the devices, furniture, and/or structures. It should also be understood that while a horizontal surface is desirable, alternative angled surfaces may be provided, as well.

As shown, an antenna layer 116 provides for the same or similar structure as the charging surface 102 such that an RF energy signal may be leaked from the charging surface 102 in response to an antenna tuned to the frequency of the RF energy signal being positioned in a near-field distance of the charging surface 102. In one embodiment, rather than the entire charging surface 112 being configured to operatively charge an electronic device, a portion of the charging surface 112 may be configured to perform the charging functionality, as described herein.

FIG. 2A illustrates a schematic diagram 200 of various components including an embodiment of the charging surface 102 of FIG. 1A. The charging surface 102 may include a housing 202, where antenna elements 204 (shown as antenna elements 204 a through 204 n), digital signal processor (DSP) or microcontroller 208, and optional communications component 210 may be included. Housing 202 can be made of any suitable material, for example plastic or hard rubber, that allows for signal or wave transmission and/or reception. Antenna elements 204 are each disposed within one of the unit cells of the charging surface 102, and may include suitable antenna types for operating in frequency bands such as 900 MHz, 2.5 GHz, or 5.8 GHz as these frequency bands conform to Federal Communications Commission (FCC) regulations part 18 (Industrial, Scientific and Medical (ISM) equipment). Other frequencies and multiple frequencies are also possible. Suitable antenna types may include, for example, patch antennas with heights from about 1/24 inch to about 1 inch and widths from about 1/24 inch to about 1 inch. Other types of antenna elements 204 may be used, for example, metamaterials and dipole antennas, among others.

In one embodiment, a microcontroller 208 may include circuitry for generating and controlling RF transmission using antenna elements 204. These RF signals may be produced using an external power supply 212 and RF circuitry (not shown) including a local oscillator chip (not shown) using a suitable piezoelectric material, filters, and other components. These RF signals are then connected to the antennas 204 and cause an RF energy signal to be present in the unit cells of the charging surface 102. Microcontroller 208 may also process information sent by a receiver through its own antenna elements for determining times for generating the RF signals and for causing the appropriate power level to be produced by the resulting RF energy signals. In some embodiments, this may be achieved using communications component 210 configured to cause the RF energy signals to be produced within a desired frequency range, as previously described and as understood in the art. In an alternative configuration, rather than using a local signal generator, a non-local signal generator (i.e., outside the charging surface 102) may be utilized.

In some embodiments, a power amplifier (not shown) and gain control circuitry (not shown) may be applied to each antenna 204. However, given the number of antennas that may be used in a charging surface 102, the use of one or more power amplifiers to amplify an RF signal (an RF signal that is supplied to or generated within the charging surface 102) in order to generate an RF energy signal (the signal that is applied to the antennas 204) to feed each of the multiple antennas 204 provides for reduced circuitry and lower cost. In one specific embodiment, four RF input ports (not shown) may be used to feed the antennas 204 of the charging surface 102. In designing the charging surface 102, a single RF input port or RF generator internal to the charging surface 102 may support a certain number or ratio of antennas 204.

In one embodiment, communications component 210 may include a standard wireless communication protocol, such as Bluetooth® or ZigBee®. In addition, communications component 210 may be used to transfer other data, such as an identifier for the electronic device 104 or surface 102, battery level, location, charge data, or other such data. Other communications components may be possible, which may include radar, infrared cameras, or frequency-sensing devices for sonic triangulation to determine the position of the electronic device 104.

In one embodiment, in response to the communications component receiving a wireless signal (e.g., Bluetooth® signal) from an electronic device to be charged by the charging surface 102, the microcontroller 208 may be notified using a digital signal 214 to responsively cause the communications component 210 to generate an RF energy signal 216 to be applied to antennas 204. In an alternative embodiment, the communications component may have its own RF circuitry and antenna(s) for receiving wireless signals, and the microcontroller causes RF energy for charging to be applied to the antennas. With such a configuration, an RF port (see FIGS. 5B and 6B) may provide for an electrical conductor to provide for an RF signal to be communicated to the communications component 210 for processing and communication to the antennas 204. In yet another embodiment, a separate device, such as battery pack, protection case of a mobile device, or any other device that may be used to charge or power an electronic device may include RF circuitry and antenna(s) for receiving wireless signals from the charging surface 102.

In one embodiment, a separate antenna (not shown) may be configured to receive RF signals and communicate the received RF signals to the communications component 210 for processing and/or directly routing to the antennas 204. The use of a separate antenna may enable the charging surface 102 to be operated remotely from a far-field transmitter that transmits an RF charging signal to the charging surface 102 for charging or powering an electronic device in a near-field manner, as described herein.

The power supply 212 may be provided by way of a connection (e.g., a USB or microUSB connection) to a laptop, wall charger, internal battery, external battery, or other power source. The power supply 212 may be used to power circuitry on or at the charging surface 102.

FIG. 2B is a flow diagram 250 illustrating general operation of the charging surface 102 in accordance with one or more embodiments of the present disclosure. At step 252, the charging surface 102 generates an RF energy signal in one or more of the unit cells of the charging surface 102. The unit cells retain substantially all (e.g., below a certain leakage threshold, such as −30 dB below the RF energy signal) of the RF energy signal used to charge the electronic device 104 when there is no electronic device 104 antenna positioned within a near-field distance from any of the antennas 204 of the unit cells or if the antenna of the electronic device 104 is not tuned or otherwise configured to receive the RF energy signal. At step 254, the unit cells adapt to allow the RF energy signal to leak from the unit cells to an antenna of the electronic device 104 when the antenna is: (i) positioned within the near-field distance from one of the unit cell antennas 204, and (ii) tuned to the frequency of the RF energy signal (or is otherwise configured to receive the RF energy signal). The adaption of the unit cells to allow leakage of the RF energy signal is a result of a capacitive inductance element (antenna) being placed in the near-field of one or more of the unit cells. This process continues to charge the electronic device 104.

FIG. 2C is a flow diagram illustrating a more detailed process 260 of the illustrative charging surface in accordance with one or more embodiments of the present disclosure. The process 260 may start at step 262, where an RF energy signal may be provided at a charging surface. The RF energy signal may be an RF energy signal that is provided at the charging surface by being contained (trapped/stored) or propagated within a substrate of the charging surface. In an alternative embodiment, rather than providing the RF energy signal at the charging surface, an RF signal that is used to cause the RF energy signal to be propagated within the substrate may be turned off until a change in capacitance, inductance, or RF signal is sensed at the charging surface by a passive or active electronic device. Still yet, the RF energy signal may be intermittently turned on or turned on at a low power level until an electronic device is determined to be proximately located or actually within the near-field of the charging surface.

At step 264, an RF antenna of an electronic device may enter a near-field of the charging surface. The near-field may be a range at which the charging surface is capable of leaking the RF energy signal from the surface in response to a capacitance and/or inductance change near the charging surface, as further described herein.

At step 266, the RF energy signal may be leaked from the charging surface in response to the RF antenna entering the near-field of the charging surface. As an example, if the amount of RF energy in the RF energy signal that is distributed and being propagated within the substrate of the charging surface is 5 W, then the RF energy signal may automatically be routed to a location (e.g., above one or more unit cells) of the antenna of the electronic device that is within the near-field of the charging surface and leaked therefrom to cause the 5 W to be applied to the antenna entering the near-field of the charging surface. As understood in the art, the amount of charge that results from being in the near-field of the charging surface is based on the amount of coupling between the two antennas. If, for example, a coupling ratio is 1, then there is 0 dB loss. If, for example, the coupling ratio is 0.5, then there is a 3 dB loss.

At step 268, when the RF antenna exits from the near-field of the charging surface, the RF energy signal stops being leaked from the charging surface at step 270. At that time, the RF energy signal again is trapped/stored within the substrate of the charging surface. Alternatively, in one embodiment, the RF signal that is applied to the charging surface to create the RF energy signal is turned off to save power.

FIG. 3A illustrates a schematic diagram 300 of various components comprising an embodiment of the electronic device 104. The electronic device 104 may include a receiver component 302, one or more antennas 304, a battery 312 that is to be charged in accordance with the present disclosure, and an optional communications component 310. In some embodiments, the communications component 310 may be included in the receiver component 302. In some embodiments, the receiver component 302 comprises circuitry including one or more switch elements 305, a rectifier 306, and a power converter 308, where the rectifier 306 and power converter 308 may be combined. The receiver 302 may be positioned within the electronic device 104 and connected to the electronic device antenna(s) 304, battery 312, and optional communications component 310. In some embodiments, the receiver component 302 may include a housing made of any suitable material, for example plastic or hard rubber that may allow for signal or wave transmission and/or reception.

The device antennas 304 may include suitable antenna types for operating in frequency bands similar to the bands described above with respect to FIG. 2A. In some embodiments, the device antennas 304 may include an antenna designed for Wi-Fi data communication with the electronic device 104, and an antenna designed for wireless data communication associated with telecommunications of the electronic device 104. The antennas 304 may be conventional and native to the electronic device 104 as produced off-the-shelf for consumer usage. In some embodiments, the device antennas 304 that operate in the frequency bands as described above serve at least two purposes. One exemplary purpose is to facilitate the data communication with the electronic device 104 over wireless standards such as Bluetooth or WLAN for communication of user data as well as for communication of data related to the wireless charging function. A second purpose is to receive the RF charging signal from a charging surface and provide this signal to the receiver component 302. In such embodiments the device antennas 304 are serving two functions, and there is no separate dedicated antenna for reception of wireless charging signal.

However, in other embodiments, the electronic device 104 may include two sets of antennas. One set of one or more antennas to facilitate wireless data communication such as over Bluetooth or WLAN for communication of user data as well as data related to wireless charging operation; a second set of one or more antennas to receive RF wireless charging signals and provide this signal to the receiver component 302. In this embodiment, one set of antenna(s) is dedicated to the reception of RF charging signal. Note that in this embodiment, use of separate set of antenna(s) allows for the data communication and RF charging to operate on different frequencies if desired.

The charging surface has a certain operating frequency band. Depending on that operating frequency band of an antenna of an electronic device 104, the antenna of the electronic device 104 is to be within the operating frequency band of the charging surface so that power transfer within the near-field may be made. As an example, if the RF frequency of the RF energy signal operates within a Wi-Fi frequency band, then antennas for mobile communications will not cause leakage of the RF energy signal due to being outside the frequency band of the charging surface. In one embodiment, a separate device, such as a power pack with an antenna, power converter, and battery, may be configured to operate at a frequency outside the frequency band of conventional mobile communications (e.g., GSM, LTE, etc.). As an example, the charging surface may be configured to operate over an unlicensed frequency band, and a power pack may be configured to also operate over that frequency band so that communications are not impacted when being charged by the charging surface.

In some embodiments, the receiver component 302 may incorporate antennas (not shown) that are used in lieu of, or in addition to, the electronic device antennas 304. In such embodiments, suitable antenna types may include patch antennas with heights from about 1/24 inch to about 1 inch and widths from about 1/24 inch to about 1 inch, or any other antenna, such as a dipole antenna, capable of receiving RF energy signals generated by the charging surface 102. Alternative dimensions may be utilized, as well, depending on the frequencies being transmitted by the antenna. In any event, regardless of whether the original device antennas 304 or additional antennas incorporated into the receiver 302 are used, the antennas should be tuned or otherwise be configured to receive the RF energy signal generated by the charging surface 102 when placed within a near-field distance from the charging surface 102. In some embodiments, the receiver component 302 may include circuitry for causing an alert signal to indicate that the RF energy signal is received. The alert signal may include, for example, a visual, audio, or physical indication. In an alternative embodiment, rather than using an antenna internal to an electronic device, a separate charging device, such as a “back pack” that may simultaneously operate as a protective case, as an example, for the electronic device (e.g., mobile phone), may include an antenna along with a power conversion electronic device that converts the RF energy signal into a DC power signal.

The switch element(s) 305 may be capable of detecting the RF energy signals received at one or more of the antennas 304, and directing the signals to the rectifier 306 when the detected signals correspond to a power level that exceeds a threshold. The switch element(s) may be formed from electronics, such as diode(s), transistor(s), or other electronic devices that may be used to determine a power level, absolute or average, that causes the switch element(s) 305 to route the signal from a receiver to the rectifier 306 for power conversion thereby. For example, in some embodiments, the switch may direct the received RF energy signals to the rectifier 306 when the RF energy signal received at the antenna 304 is indicative of a wireless power transfer greater than 10 mW. In other embodiments, the switch may direct the received RF energy signals when they are indicative of a wireless power transfer greater than 25 mW. This switching acts to protect from damaging electronic components, such as a receiver circuit, of the electronic device 104 by preventing a power surge from being applied thereto. If the threshold power is not reached, the electronic device operates in a conventional manner.

The rectifier 306 may include diodes, resistors, inductors, and/or capacitors to rectify alternating current (AC) voltage generated by antennas 304 to direct current (DC) voltage, as understood in the art. In some embodiments, the rectifier 306 and switch 305 may be placed as close as is technically possible to the antenna element 304 to minimize losses. After rectifying AC voltage, DC voltage may be regulated and/or conditioned using power converter 308. Power converter 308 can be a DC-DC converter, which may help provide a constant voltage output, regardless of input, to an electronic device or, as in this embodiment, to a battery 312. Typical voltage outputs can be from about 0.5 volts to about 10 volts. Other voltage output levels may be utilized, as well.

Optional communications component 310, similar to that described above with respect to FIG. 2A, may be included in electronic device 104 to communicate with the communications component 210 and other electronic equipment. The communications component 310 may be integrated with the receiver component 302 or may be a discrete component located in the electronic device 104. In some embodiments, the communications component 310 may be based on standard wireless communication protocols, which may include Bluetooth® or ZigBee®. In addition, communications component 310 may be used to communicate other data, such as an identifier for the electronic device 104 or charging surface 102, battery level, location, power requirements specific to the electronic device 104, or other data.

FIG. 3B is a flow diagram 350 illustrating general operation of the electronic device 104 in accordance with one or more embodiments of the present disclosure. At step 352, the antenna 304 receives an RF energy signal from one or more of the unit cells of the charging surface 102 when the antenna 304 is tuned to the frequency of the RF energy signal (or is otherwise configured to receive the RF energy signal) and is positioned within a near-field distance from one or more of the antennas 204 of the unit cells. At step 354, the receiver component 302 converts the received RF energy signal to a power signal that is used to charge the device battery 312 at step 356. Alternatively, rather than charging a battery, the power signal may power circuitry of the electronic device directly, thereby enabling the electronic device to be operated independently of a battery.

FIG. 4A illustrates a schematic diagram of an electrical circuit model 400 a representing the electrical state of the charging surface 102 when the electronic device 104 is not positioned within the near-field distance from the charging surface 102. The electrical circuit model 400 a includes circuitry 402 representative of the electromagnetic operation of the charging surface 102 when no electronic device antenna 304 is positioned in a near-field distance from the charging surface 102. The electrical circuit model 400 a represents a model of the charging surface 102 that is configured not to leak or otherwise output RF signals due to not being tuned or otherwise operating as high-impedance prior without an antenna of an electronic device being positioned within the near-field distance of the charging surface 102.

FIG. 4B illustrates a schematic diagram of an electrical circuit model 400 b representing an electrical connection between the charging surface 102 and the electronic device 104 when the electronic device 104 is positioned within the near-field distance from the charging surface 102 and the antenna(s) 304 of the electronic device 104 is tuned to the center frequency of the RF energy signal generated by the charging surface 102. The electrical circuit model includes circuitry 404 representative of the electronic device 104 being electromagnetically coupled to the circuitry 402 of the charging surface 102 to cause a change in the electromagnetic operation of the charging surface 102. The electrical circuit model 400 b represents a model of the charging surface 102 that is configured to leak or otherwise output RF signals when an antenna of an electronic device is positioned within the near-field distance of the charging surface 102 so as to cause the representative electrical circuit model 400 b to become tuned due to coupling effects, as understood in the art and further described with regard to FIGS. 4C and 4D.

FIG. 4C shows schematic models of equivalent circuits with two states of energy flow without and with an electronic device positioned in a near-field distance of the charging surface. In the first state, air causes a reflection of energy from a high impedance surface of the charging surface. In the second state, inclusion of an antenna receiver in a near-field of the surface forms an inductive coupling that enables energy flow through the high impedance surface of the charging surface. FIG. 4D is an illustration of an alternative representation of the schematic models of FIG. 4C. It should be understood that the models in FIGS. 4C and 4D are simplified and more complex models may be utilized to represent the adaptive high-impedance surface.

Referring now to FIGS. 5A-5D, an example embodiment of an antenna portion 500 of a charging surface is provided, wherein the antenna portion 500 includes a plurality of unit cells 502 arranged in a matrix formation. Each of the unit cells 502 includes two substrate layers 515 a and 515 b. The top substrate layer 515 a of each of the unit cells 502 includes a metal portion 504 (e.g., copper) defining apertures 506 positioned at the top of the unit cells 502. The bottom substrate layer 515 b of each unit cell 502 includes a patch antenna 510 comprising a metal patch 512 having an electrical connection through a via 508 to a ground plane 514. The ground plane 514 may be a metamaterial. The ground plane 514 is connected to an RF port 505 as shown in FIG. 5B for conducting RF signals to unit cells 502.

In some embodiments, the patch antenna 510 is configured to generate the RF energy signal that radiates within the top substrate layer 515 a. In accordance with the present disclosure, the RF energy signal remains in the top substrate layer 515 a until the RF energy signal decays or is leaked to an antenna 304 (FIG. 3) of an electronic device positioned on a charging surface.

In some embodiments, the size of the aperture 506 is determined in accordance with the periodic frequency of the RF energy signal such that the RF energy signal does not leak from the aperture 506 in the unit cells 502 unless an antenna tuned to the frequency of the RF energy signal is positioned in a near-field distance (e.g., less than about 4 mm) from at least one of the unit cells 502.

Referring now to FIGS. 6A-6D, an example embodiment of an antenna portion 600 of a charging surface is provided, where the antenna portion 600 is composed of a plurality of unit cells 602 arranged in a matrix formation. Each of the unit cells 602 includes one substrate layer 615 having a metal portion 604 (e.g., copper) defining an aperture 606 positioned at the top of the unit cells 602. The unit cells 602 also include a patch antenna 610 formed by a metal patch 612 having an electrical connection through a via 608 to a ground plane 614. The ground plane 614 may be physically and electrically connected to an RF port 605, as shown in FIG. 6B. The RF port 605 may be used to provide an RF energy signal from an RF energy signal generator to be applied to each of the unit cells 602, and the ground plane 614 may be electrically connected to a ground portion of the RF port 605.

In the embodiment illustrated in FIGS. 6A-6D, the patch antenna 610 is positioned within the unit cell 602 such that the aperture 606 is formed around a perimeter of the metal patch 612. In some embodiments, the patch antenna 610 is configured to propagate the RF energy signal from the top surface of the substrate layer 615. In accordance with the present disclosure, the RF energy signal remains at or near the top surface of the substrate layer 615 until the RF energy signal decays or is received by the electronic device antenna 304.

In some embodiments, the size of the aperture 606 is determined in accordance with the periodic frequency of the RF energy signal generated by the patch antenna 610 such that the RF energy signal does not or has minimal leakage from the aperture 606 of the unit cells 602 unless an antenna tuned to the frequency of the RF energy signal is positioned in a near-field distance from at least one of the unit cells 602. The aperture 606 may be altered in dimension depending on frequency of the RF energy signal so as to be properly tuned for preventing leakage of the RF energy signal when no electronic device is positioned in the near-field. It should be understood that a number of layers of the unit cell may vary depending on the application, where different number of layers may provide different responses from the unit cells to provide different harmonic responses (e.g., higher or shifted harmonic frequencies for different wireless powering applications).

FIG. 6E is an illustration of a cross-sectional view of an illustrative charging surface 620 inclusive of a plurality of unit cells 622 a-622 n (collectively 622). The unit cells 622 include vias 624, patches or slots 626, substrate 628, and surface element 630. The surface element 630 include a plurality of holes or patches 632 a-632 n (collectively 632). In one embodiment, the length and width of the unit cells 622 are between about 5 mm and about 10 mm. It should be understood that alternative dimensions may be utilized as a function of the frequency being propagated or trapped/stored by the unit cells and/or the material being used to form the surface 622. The substrate 628 may be formed of Rogers FR-4, ceramic, or other material. The use of a substrate 628, such as ceramic, allows for the dimensions of the unit cells to be smaller than otherwise possible without a substrate 628.

Resonance

A resonant coupler may be formed when a device to be charged itself enables transmission of power and operates as part of a charging system. For example, a mobile telephone having a metallic case may be utilized to complete a charging device, as further described in FIGS. 7A and 8A-8C. The charging system may work in two different stages. A first stage may provide for a field being fed through a feeding point (e.g., slot on a ground plane) into a first cavity and getting trapped in the structure of the first cavity. The first cavity may include a number of touch/leak points that are activated when being touched by or proximately close to an electronic device with a metal case. A second stage may operate when the electronic device is placed on the surface at a touch point so that energy leaks out of the second cavity formed in part by the electronic device on top of the charging surface.

FIGS. 7A, 8A-8C illustrate a cross-sectional view of the electronic device 104 positioned a distance D within a near-field distance D_(NF) from a charging surface 700, in accordance with an embodiment of the present disclosure. Thus, in accordance with the present embodiment, the antenna(s) 304 of the electronic device 104 are positioned a distance D, which is within the near-field distance D_(NF). The RF energy signals generated by the charging surface 700 in the near-field do not achieve a particular polarization before being received by the antenna(s) 304 of the electronic device 104. In some embodiments, the near-field distance D_(NF) is less than approximately 4 mm.

In the embodiment illustrated in FIGS. 7A and 8A-8C, the electronic device 104 includes a back surface 701 that is generally formed of metallic surfaces 702 a, 702 b, and 702 c and includes defining gaps 704 a and 704 b that are non-metallic and that may be formed of a plastic, glass, or any other material suitable to allow signal or wave transmission and/or reception. The gaps 704 a and 704 b are located proximate the antennas 304 such that the antennas 304 may receive signals entering through the gaps 704 a and 704 b. The metallic surfaces 702 a, 702 b, and 702 c reflect RF energy signals 802, as shown in FIG. 8A, such that the RF energy signal 802 generated by the charging surface 700 traverses or resonates within a cavity 706 formed between a top surface 708 of the charging surface 700 and one or more of the metallic surfaces 702 a, 702 b, and 702 c until it reaches at least one of the gaps 704 a and 704 b. The RF energy signal 802 traverses or resonates between the metal surface 702 b, for example, and top surface of the charging surface 700 as a trapped wave in the cavity 706 (see FIG. 8A, RF energy signal 802 reflecting between the two surfaces). The gaps 704 a and 704 b are positioned above the charging surface 700, and more specifically, one or more unit cells of the charging surface 700, so that the RF energy signal 802 can traverse the cavity 706 to reach one of the gaps 704 a and 704 b. When the RF energy signal 802 reaches the gap 704 a, the RF energy signal 802 enters through the gap 704 a and is received by the device antenna 304.

More particularly, as shown in FIGS. 8B and 8C, the charging surface 700 is shown to include a cover 802 within which a first cavity 804 a and a second cavity 804 b (collectively 804) are formed by a ground plane 806 that separates the two cavities 804. The ground plane may be formed of metamaterial, as described herein. The charging surface 700 may also include one or more touch points 810 from which an RF energy signal emanates. In operation, a first stage may provide for an RF energy signal being fed through a feeding point (e.g., slot on a ground plane) into the first cavity 804 a and gets trapped in the structure of the first cavity 804 a. The first cavity 804 a may include a number of touch/leak points 810 that are activated when being touched by or proximately close to an electronic device with a metal case. A second stage may operate when the electronic device is placed on the cover 802 at at least one of the touch points 810 so that energy leaks out of the second cavity 804 b formed in part by the electronic device on top of the cover 802 of the charging surface 700. Because only a few touch points 810 are utilized in this charging surface 700, fewer power amplifiers are needed to supply RF energy signals, thereby costing less than having many more touch points. In one embodiment, four touch points 810 may be utilized. However, it should be understood that the number of touch points may vary depending on the size of the area provided by the charging surface 700. If a large area (e.g., desk) is provided, then more touch points 810 are provided. If a smaller area (e.g., pad) is provided, then fewer touch points 810 are provided.

In some embodiments, such as that shown in FIGS. 7A and 8A, the metallic surfaces 702 a, 702 b, and 702 c are positioned substantially parallel to the top surface 708 of the charging surface 700. Although the RF energy signal 802 is represented in FIG. 8A as having a triangle waveform reflection, it should be appreciated that the RF energy signal 802 may be reflected in other patterns, as understood in the art. As used herein, “traverses” refers to the RF energy signal travelling along or through a space or cavity by reflecting off of surfaces.

FIG. 8D shows the electronic device 104 being placed on the charging surface 700. As the electronic is placed on the charging surface 700, energy flow 812 from an RF energy signal is created in the cavity formed by the electronic device 104 and the charging surface.

FIG. 7B illustrates an illustrative electronic schematic of the electronic device 104 of FIG. 7A. The electronic device 104 is shown to include the two gaps 704 within which the antennas 304 are positioned to receive RF signals 706. The antennas 304 are in electrical communication with an RF integrated circuit (RF-IC) 708 via electrical conductor 710. The RF-IC 708 is shown to include a switch 712 and rectifier device 714. The switch 712 may be configured to cause the RF signals 706 to be routed to a transceiver (XCVR) 716 when communications signals. The transceiver 716 is a conventional transceiver used for user communications, as understood in the art. However, in response to the RF signals 706 crossing a certain threshold level, such as 0.1 W or 0.25 W, the switch 712 may be activated to cause the RF signals 706 to be routed to the rectifier device 714 that includes one or more rectifiers 718 therein. The switch 712 may be a solid state switch, as understood in the art. An output from the rectifier device 714 may be routed to a battery 720 used to power the electronic device 104.

Referring now to FIG. 9, an example method is shown in flow diagram 900 for charging the electronic device 104 with the charging surface 700 in accordance with an embodiment of the present disclosure. In the embodiment illustrated in FIG. 9, the charging surface 102 communicates with the electronic device 104 via respective communication components 210 and 310. At step 902, the charging surface communication component 210 receives, from the electronic device communication component 310, a signal indicative of a request to charge the electronic device 104. In some embodiments, this signal may include, for example, an identification of the electronic device 104, a battery level, power requirements of the electronic device 104, or other information. For example, in some instances, the electronic device 104 may be a device having a lower power requirement, such as, for example, a smart-watch or other wearable technology. In order to avoid receiving a large power surge that would damage the smart-watch, the charge request could include a power limit, such as, 0.5 W. Alternative power levels may be utilized, as well. Similarly, the electronic device 104 may have a larger power requirement. In such cases, the charge request could include the larger power requirement, such as 5 W, for charging the electronic device 104.

Rather than receiving an active charge request, the charging surface may receive or sense any wireless or radiation signal from an electronic device that indicates that an electronic device is proximate to the charging surface, including but not limited to the presence or absence of reflection of an RF energy signal transmitted by the charging surface. Any receiver or sensor may be utilized to sense such a signal from an electronic device. In an alternative embodiment, a proximity switch or pressure switch may be utilized to detect that an electronic device is proximate to or positioned on the charging surface. Still yet, a magnetic switch or light switch may be utilized.

At step 904, the microcontroller 208 initiates generation of an RF energy signal in accordance with the data provided in the charge request. For example, if the charge request indicates the power requirements of the electronic device 104, then the microcontroller 208 causes the RF energy signal to be generated such that the power transmitted to the electronic device 104 complies with the power requirements communicated in the charge request. In accordance with the above example of a smart-watch, the microcontroller 208 may cause the charging surface 700 to generate an RF energy signal capable of providing wireless power transfer of 0.5 W to the smart-watch. In one embodiment, if an electronic device is sensed, then an RF energy signal may be generated.

As discussed herein, the RF energy signal is generated in the unit cells of the charging surface 700, and substantially remains in the unit cells until the RF energy signal decays or is leaked. When an antenna 304 tuned to the frequency of the RF energy signal is placed within a near-field distance from one or more of the unit cells, those unit cell(s) allow the RF energy signal to leak to the antenna 304 at step 906.

As step 908, the leaked RF energy signal is received at the antenna(s) 304 tuned to the frequency of the RF energy signal and placed within the near-field distance from the unit cell(s).

At step 910, the received RF energy signal is converted to a power signal to charge the battery 312 of the electronic device 104. This step may include detecting the RF energy signal received at the antenna 304, activating the switch mechanism 305 when the RF energy signal is indicative of a power signal greater than the threshold value (e.g., 10 mW) rectifying the signal via the rectifier 306, and converting the rectified signal to a DC power signal via the converter 308. The power signal is then used to charge or operate the electronic device battery 312 at step 912.

Although it is not illustrated in the flow diagram 900, the communications component 310 may, in some embodiments, transmit a signal to the charging surface 700 to request that the charging be suspended or discontinued. This may happen, for example, if the battery 312 of the electronic device 104 is completely charged or reaches a desired charge level, the electronic device 104 is being turned off, the communications component 310 is being turned off or moved out of communication range with the communications component 210, or for other reasons. In another embodiment, in the event that the electronic device is no longer being sensed, electronically, physically or otherwise depending on the sensor being utilized, then the communications component 210 may be turned off.

Referring now to FIG. 10, an example method is shown in flow diagram 1000 for sensing the presence of and charging the electronic device 104 with the charging surface 700 in accordance with an embodiment of the present disclosure. In the embodiment illustrated in FIG. 10, the electronic device 104 does not communicate with the charging surface 102 via respective communication components 210 and 310. This embodiment is representative of instances where the electronic device 104 is turned off, has a drained battery, or is otherwise unable to communicate with the charging surface 700. Thus, in the present embodiment, the charging surface 700 operates in a manner so as to avoid flooding an undetected electronic device 104 with excessive power. This is the manner that a receiver with a dead battery, and hence no ability to communicate with the transmitter, may be charged.

At step 1002, the charging surface 700 generates a low-power RF energy signal, which is an RF energy signal capable of providing wireless, low-power transmission to an electronic device 104. Specifically, the microcontroller 208 initiates generation of the low-power RF energy signal such that the power capable of being transmitted via the low-power RF energy signal is “low-power.” For example, in some embodiments, low-power is 1 W. Alternative power levels may be utilized, as well. In some embodiments, detecting that an electronic device is positioned within a near-field distance of the charging surface may be accomplished by activating the unit cell patch antennas 204 with a 1% duty cycle.

In accordance with the present disclosure, the low-power RF energy signal is generated in the unit cells of the charging surface 700, and remains in the unit cells until the low-power RF energy signal decays or is leaked. When an antenna 304 (of a receiver) tuned to the frequency of the low-power RF energy signal is placed within a near-field distance from one or more of the unit cells, those unit cells allow the RF energy signal to leak to the antenna 304 at step 1004.

At step 1006, the microcontroller 208 may sense the low-power RF energy signal present in the unit cells. For example, in some embodiments, the microcontroller 208 may include sensing circuitry, such as, an RF coupler capable of detecting a “reflection” of the low-power RF energy signal, where the reflection is representative of, for example, approximately 10% of the low-power RF energy signal present in the unit cells. The microcontroller 208 may, therefore, calculate the low-power RF energy signal present in the unit cells based on the reflected value sensed by the microcontroller 208. Although the sensing performed at step 1006 is illustrated in a sequential order in FIG. 10, it should be appreciated that this step may be performed in any order or repeated continuously in parallel with the processes performed in the flow diagram 1000. The low-power RF energy signal may be generated periodically or aperiodically in a pulsed or other manner to determine if an electronic device is present, as indicated in the diagram 1000.

Once the microcontroller 208 senses the low-power RF energy signal present in the unit cells, the sensed low-power RF energy is compared to a threshold value at step 1008 to determine whether to generate a subsequent low-power RF energy signal within the unit cells. Instances in which the sensed low-power RF energy signal is less than the threshold value are indicative of a situation in which the low-power RF energy signal has either decayed or leaked to an antenna tuned to the frequency of the low-power RF energy signal and positioned within a near-field distance from one or more of the unit cells. Thus, if the sensed low-power RF energy signal is less than the threshold, it is presumed the low-power RF energy signal has either leaked or decayed, so the process returns to step 1002 and the microcontroller 208 activates the antennas 204 to generate a subsequent low-power RF energy signal. Otherwise, when the reflection is above the threshold, the low-power RF energy signal remains in the substrate and subsequent RF signals are not generated so that the unit cells of the charging surface 700 do not continue to build up energy. Accordingly, the process returns to step 1006, and the microcontroller 208 continues to sense the low-power RF energy signal present in the unit cells.

The method illustrated in FIG. 10 is indicative of a situation in which no communication component 310 is communicating with the charging surface 700. For example, the battery 312 of the electronic device 104 may be too depleted to activate the communication component 310. However, once the battery 312 has sufficient charge, the electronic device 104 may, in some embodiments, activate the communication component 310. At that time, the communication component 310 may initiate communication with the communication component 210 of the charging surface 700, and the charging surface 700 may switch to the charging method illustrated in FIG. 9 and described above.

Harmonic Filter

In conventional power-transmission systems, various electronic elements that form the system are often lumped together, and losses experienced by each lumped element are compounded such that the system, as a whole, experiences a larger loss than each of the elements individually. For example, if a system has an antenna that is 90% efficient lumped with an amplifier that is 90% efficient, then the combined efficiency of a system comprising these two elements is approximately 81%. As more elements are added, the overall efficiency of the system is further reduced. Accordingly, in order to increase the efficiency of the disclosed charging surface, some embodiments of the charging surface may include filter elements such as, a harmonic filter, to reduce the radiated energy in frequencies other than the intended wireless charging signal, and specifically to reduce the energy in the harmonics of the intended wireless charging signal. A harmonic filter may, for example, attenuate these frequency components by 40 dB to 70 dB

FIG. 11A and FIG. 11B illustrate perspective and cross-sectional views, respectively, of a representative unit cell 1102 comprising an embodiment of the charging surface 102, where each unit cell 1102 has a harmonic filter element 1104 positioned on a top surface of the unit cell 1102. The unit cell 1102 illustrated in FIGS. 11A and 11B is similar to that described above and shown in FIGS. 6A-6D, however, the harmonic filter element 1104 may be placed on a top surface of unit cells of a different embodiment, such as the embodiment described above and illustrated in FIGS. 5A-5D.

It should be appreciated that the harmonic filter element 1104 included in each unit cell 1102 may be a discrete filter element, or it may be a portion of a larger, single harmonic filter element spanning the top surfaces of multiple unit cells 1102 forming the charging surface 102. Thus, the charging surface 102 includes, in such embodiments, a harmonic filter element 1104 placed over the unit cells 1102 such that the charging surface 102 includes a harmonic filter positioned over a matrix (or array) of transmit antennas (e.g., patch antennas 610).

In the embodiment illustrated in FIGS. 11A and 11B, each of the unit cells 1102 includes a single substrate layer 615, and the harmonic filter element 1104 present in each of the unit cells 1102 comprises a single harmonic filter element spanning the entire top surface area of the unit cells 1102. In other embodiments, however, the harmonic filter element 1104 may include multiple harmonic filter elements, where one of the multiple harmonic filter elements are disposed on a top surface of one of the elements forming the unit cells 1102. It should be understood that the unit cell with the harmonic rejection filter may be formed by a more complex unit cell, such as a unit cell that includes more layers and features within the unit cell. For example, this latter embodiment could be represented by a harmonic filter element 1104 placed on the top surface area of the patch antenna 610, a harmonic filter element 1104 placed on the top surface area of the metal portion 604, and no harmonic filter element covering the aperture 606.

In some embodiments, the harmonic filter element 1104 is formed of two or more screen layers, wherein each layer includes a screen to filter out specific harmonics of the intended wireless charging signal. The harmonic filter 1104 acts to filter the RF energy signal generated by the patch antenna 610 such that the RF energy signal operates at a particular frequency (also referred to herein as a center frequency). As a result of the harmonic filter element 1104 being a passive mechanical device, loss in signal power is reduced as compared with an electronic filter.

FIGS. 12A and 12B illustrate perspective and cross-sectional views, respectively, of a representative unit cell 1202 comprising an embodiment of the charging surface 102, where each unit cell 1202 has a harmonic filter element 1204 positioned within a top substrate layer 515 a of the unit cell 1202 (or optionally between the top substrate layer 515 a and a bottom substrate layer 515 b). It should be appreciated that the harmonic filter element 1204 included in each unit cell 1202 may be a discrete filter element, or it may be a portion of a larger, single harmonic filter element spanning the top substrate layers 515 a of multiple unit cells 1202 forming the charging surface 102. Thus, the charging surface 102 includes, in such embodiments, a harmonic filter element 1204 placed within the top substrate layers 515 a of the unit cells 1202 such that the charging surface 102 includes a harmonic filter positioned over a matrix (or array) of transmit antennas (e.g., patch antennas 510).

In the embodiment illustrated in FIGS. 12A and 12B, the unit cells 1202 include a top substrate layer 515 a and a bottom substrate layer 515 b, and the harmonic filter element 1204 present in the top substrate layer 515 a of each of the unit cells 1202 comprises a single harmonic filter element spanning the entire area of the top substrate layer 515 a of the unit cells 1202. In other embodiments, however, the harmonic filter element 1204 may span only a portion of the top substrate layer 515 a such that the harmonic filter element 1204 is disposed above only the patch antenna 510, which is located in the bottom substrate layer 515 b.

In some embodiments, the harmonic filter element 1204 is formed of two or more screen layers, wherein each layer includes a screen to filter out specific harmonics of the intended wireless charging signal. The harmonic filter 1204 acts to filter the RF energy signal generated by the patch antenna 510 such that the RF energy signal operates at a particular frequency (also referred to herein as a center frequency). As a result of the harmonic filter element 1204 being a passive mechanical device, loss in signal power is reduced as compared with an electronic filter.

Receiver Device Stacking

FIGS. 13A and 13B show components of a wireless charging system 1300 among a plurality of electronic devices 1302, 1304, according to exemplary embodiments. For ease of explanation, FIG. 13A and FIG. 13B show wireless power transfer among two devices 1302, 1304. However, it will be appreciated by a person having ordinary skill in the art that wireless power transfer as described herein may occur among two or more electronic devices. In the exemplary embodiment, a first electronic device 1302 may receive power from a charging surface 1306 through near-field charging techniques, and may then, in turn, provide power to a second electronic device 1304. In an alternative embodiment, the first electronic device 1302 may receive power using other techniques, such as far-field RF power transmission.

As shown in FIG. 13A, in some embodiments, the electronic devices 1302, 1304 may be stacked or otherwise placed in contact with one another to effectuate the transfer of power from the charging surface 1306 to the first device 1302, and then from the first device 1302 to the second device 1304. As shown in FIG. 13B, the first device 1302 may receive power from the charging surface 1306 using near-field power transfer techniques, and then the first device 1302 may transfer power to the second device 1304 using far-field power transfer techniques.

Near-field RF power transmission techniques may include a transmitter-side charging surface 1306 comprising a number of physical layers, such as a substrate or cavity for trapping RF energy and a top surface on which to place an electronic device 1302, 1304. A near-field charging surface may be configured to introduce RF energy into a substrate or cavity layer, where the RF energy remains trapped until some physical condition is introduced by a receiver-side antenna or electronic device 1302, 1304. In some implementations, the RF energy will be leaked through the surface of the charging surface 1306 only when an electronic device 1302, 1304 having an appropriately tuned receiver-side antenna is placed close enough for the top surface to release the RF energy. In some implementations, the RF energy remains “trapped” within the substrate or cavity layer until the metal of an electronic device 1302, 1304 contacts the surface layer. Other possible techniques may be used, though near-field techniques may generally refer to such systems and methods where the RF energy remains trapped within the charging surface 1306 until some physical condition is satisfied by a receiver-side electronic device 1302, 1304 or receiver-side antenna. In many instances, this may have an operational distance ranging from direct contact to about 10 millimeters. For example, where the operation distance is one millimeter, the first electronic device 1302 would need to be within one millimeter before the RF energy will be leaked from the substrate or cavity layer of the charging surface 1306.

Far-field RF power transmission techniques may include circumstances where a transmit-side device comprises an array of one or more antennas (not shown) configured to transmit RF power waves over some distance, which may range from less than an inch to more than fifty feet. In proximity far-field power transmission, the transmit-side device may be configured to transmit the power waves within a limited distance, such as less than twelve inches. This may be limited in any number of ways, such as requiring a receiver-side device to enter a proximity threshold from the transmit-side device before the transmit-side device will transmit power waves, or limiting the effective range for the power waves to deliver power. In some implementations, a transmit-side device functioning as a proximity transmitter may transmit the power waves to converge at or near a particular location so that the power waves generate constructive interference patterns. A receiver-side device may comprise an antenna and circuitry capable of receiving the resulting energy at the constructive interference patterns, and may then convert the energy to useable alternating current (AC) or direct current (DC) power for an electronic device coupled to the receiver device or comprising the receiver device.

Electronic devices 1302, 1304 may be any electronic device comprising near-field and/or far-field antennas capable of performing the various processes and tasks described herein. For instance, the first device 1302 and the second device 1304 may comprise antennas and circuitry configured to generate, transmit and/or receive RF energy using RF signals. In FIGS. 13A and 13B, the first device 1302 and the second device 1304 are shown as cellular phones. However, this should be not considered to be limiting upon possible electronic devices 1302, 1304. Non-limiting examples of possible electronic devices 1302, 1304 may include tablets, laptops, cell phones, PDAs, smart watches, fitness devices, headsets, or any other device capable of being recharged or operated utilizing the principles described herein.

A charging surface 1306 may generate one or more RF energy signals for wireless power transmission that are trapped in a substrate or cavity beneath a top surface of the charging surface 1306. The trapped RF energy may be leaked through the top surface and received by the first device 1302 when an appropriately tuned antenna of the first device 1302 is positioned within a near-field distance (e.g., less than approximately 10 mm) from the charging surface 1306. The appropriately tuned antenna of the first device 1302 may thus cause the RF signals trapped within the charging surface 1306 to be leaked or emitted through the charging surface 1306 to the antenna of the first device 1302. The received RF energy signals are then converted to a power signal by a power conversion circuit (e.g., rectifier circuit) for providing power to or charging a battery of the first device 1302. In the exemplary embodiments shown in FIGS. 13A and 13B, the charging surface 1306 may be shown as a box-shaped device, but it should be understood that the charging surface 1306 may have any form-factor, configuration, and/or shape. In some embodiments, the total power output by the charging surface 1306 is less than or equal to 1 Watt to conform to Federal Communications Commission (FCC) regulations part 15 (low-power, non-licensed transmitters).

Similar to the manner in which the charging surface 1306 may function as a transmitter-side device in relation to the first electronic device 1302, the first electronic device 1302 may be configured to likewise function as a transmitter-side device in relation to a second electronic device 1304.

As shown in FIG. 13A, in some embodiments, the first device 1302 may comprise components for a near field RF charging surface, similar to the charging surface 1306, allowing RF energy signals to be trapped beneath a surface layer of the first device 1302 until an appropriately tuned antenna of a second device 1304 causes the RF energy to be leaked into the antenna of the second device 1304.

Additionally or alternatively, as shown in FIG. 13B, in some implementations, the first device 1302 may be configured to function as a far-field proximity transmitter comprising an array of one or more antennas configured to transmit one or more power waves to an antenna of the second electronic device 1304.

In some embodiments, the first device 1302 may include a communications component (not shown) to effectuate wireless and/or wired communications to and from other devices, such as the second device 1304. In some cases, a communications component may be an embedded component of the first device 1302; and, in some cases, the communications component may be attached to the first device 1302 through any wired or wireless communications medium. The communications component may comprise electromechanical components (e.g., processor, antenna) that allow the communications component to communicate communications signals containing various types of data and messages with other devices, such as the second device 1304. These communications signals may represent a distinct channel for hosting communications where data may be communicated using any number of wired or wireless protocols and associated hardware and software technology. The communications component may operate based on any number of communication protocols, such as Bluetooth®, Wireless Fidelity (Wi-Fi), Near-Field Communications (NFC), ZigBee, and others. However, it should be appreciated that the communication component is not limited to radio-frequency based technologies, but may include radar, infrared, and sound devices for sonic triangulation of other devices, like the second device 1304.

In operation, the communications component of the first device 1302 may receive communications signals from the second mobile device 1304, where the communications signals contain data that includes a request to receive power from the first device 1302. Additionally or alternatively, the first electronic device 1302 may receive one or more wireless broadcasted messages from the second device 1304, thereby allowing the first electronic device 1302 to detect the presence of the second electronic device 1304 and begin sending power to the second electronic device 1304, or to begin flooding a substrate or cavity layer with RF energy. Such request messages may also include data related to the type of device, battery details of the device, such as battery type and present battery charge, and present location of the device. In some implementations, the first electronic device 1302 may use the data contained within the messages to determine various operational parameters for transmitting or otherwise transferring RF energy to the second device 1304, which the second device 1304 may capture and convert the RF energy into useable alternating current (AC) or direct current (DC) electricity.

For example, when the first device 1302 functions as a near-field charging surface, the first device 1302 may be configured to send power (e.g., engage, turn on, wake up) to a near-field charging surface within the first device 1302 when the communications component of the first electronic device 1302 receives a communications signal having a threshold signal strength indicating that the second device 1304 is within a threshold distance.

As another example, where the first device 1302 functions as a far-field proximity transmitter, the first device 1302 may use the communications signal receive data from the second device 1304 that may be used by the first device 1302 to identify the location of second device 1304 and to determine whether the second electronic device 1304 is within a threshold distance from the first device 1304.

Similarly, a communications component of the second device 1304 may use a communications signal to communicate data that may be used to, for example, send or otherwise broadcast a message to the first device 1302 requesting the first device 1302 to transfer power; the messages may also include, for example, battery power information, data indicating present location, data information about the user of the second device 1304, information about the second device 1304 to be charged, indicate the effectiveness of the power being received, and a request to stop sending the power, as well as other types of useful data. Non-limiting examples of the various types of information that may be included in communications signals may also include a beacon message, a device identifier (device ID) for first device 1302, a user identifier (user ID) for the first device 1302, the battery level for the second device 1304, the second device 1304 location, and other such information.

In some cases, when the second device 1304 enters a near-field distance of the first device 1302 in which the RF energy can be leaked and emitted from the first device 1302 into the second device 1304, the devices may establish a communications channel according to the wireless or wired communications protocol (e.g. Bluetooth®) employed by the respective communications components of the respective devices 1302, 1304. In some cases, the second device 1304 may establish a communication channel with the first device 1302 upon entering the effective communications distance of the first device 1302 of the wired or wireless communications protocols employed by the communications components. A near-field distance may be defined as a minimum distance between a transmitter-side device (e.g., charging surface 1306) and a receiver-side device (e.g., first electronic device 1302) that would cause the transmitter-side device to leak and transfer trapped RF wave signals into the appropriately tuned receiver-side device. This near-field distance may range from direct contact to about 10 millimeters. In some cases, a proximate far-field distance may be the minimum distance between a transmitter-side device to transmit one or more power waves to a receiver-side device, which may range up to about 12 inches. In an alternative embodiment, any far-field distance can be used.

The antennas of the second device 1304 may capture energy from the RF signals leaked or emitted from the first device 1302 or from the power waves transmitted from the first device 1302. After RF signals are received from the power waves or from the leakage, from either the charging surface 1306 or the first device 1302, circuitry and other components (e.g., integrated circuits, amplifiers, rectifiers, voltage conditioner) of both the first and second devices 1302, 1304 may then convert the energy of the RF signals (e.g., radio frequency electromagnetic radiation) to electrical energy (i.e., electricity), which may be stored into a battery or may power the respective electronic device 1302, 1304. In some cases, for example, a rectifier of a second device 1304 may convert the electrical energy from AC to DC form, usable by the second device 1304. Other types of conditioning may be applied as well, in addition or as an alternative to, conversion from AC to DC. For example, a voltage conditioning circuit, such as a voltage regulator, may increase or decrease the voltage of the electrical energy as required by the second device 1304.

In an alternate embodiment, the first device 1302 may also send a charging request to the second device 1304. The charging request may include data related to user of the first device 1302, details of the first device 1302, battery charge of the first device 1304, current location of the first device 1302. Upon receiving a charging request, the second device 1304 may accept or decline the request. The second device 1304 may also request additional details related to but not limited to user of the first device 1302, details of the first device 1302, battery charge of the first device 1302, current location of the first device 1302, if such details were not present with the request. On accepting the request, the second device 1304 may determine the location of the first device 1302. The second device 1304 may use one or more technologies such as sensor detection, heat-mapping detection, and others to determine the location of the first device 1302. Once the location of the first device 1302 is determined, then the second device 1304 may transmit RF signals to the first device 1302, which may be captured by antennas and/or circuitry of the first device 1302 to charge a battery of the first device 1302.

Referring again to FIG. 13A, in some embodiments, the first device 1302 and the second device 1304 may be placed on top of each other to transfer power from one or another, with or without the presence of charging surface 1306. In another embodiment, the first device 1302 and the second device 1304 may be on same plane and proximate to each other to transfer power from one or another device as depicted in FIG. 13B. It will be appreciated by a person with ordinarily skill in the art that the power transfer between the first device 1302 and the second device 1304 will occur when the devices are in near-field distances from each other irrespective of their placement with respect to each other.

In an embodiment, the first device 1302 may receive power from the charging surface 1306, and at the same time transfer the power to the second device 1304 in its near-field. In another embodiment, the first device 1302 may receive power from any suitable source of receiving power (for example, far-field antennas) and at the same time transfer the power to the second device 1304 within a near-field distance. In yet another embodiment, the first device 1302 and the second device 1304 may transfer power to a third device in their near-field. In yet another embodiment, each of the first device 1302 and the second device 1304 independently or collectively transfer power to two or more devices in their near-field.

FIGS. 14A and 14B show components of a wireless charging system 1400 among a plurality of electronic devices 1402, 1404, according to exemplary embodiments. For ease of explanation, FIG. 14A and FIG. 14B show wireless power transfer among two devices 1402, 1404. However, it will be appreciated by a person having ordinary skill in the art that wireless power transfer as described herein may occur among two or more electronic devices. In the exemplary embodiment, a first electronic device 1402 may provide power to a second electronic device 1404. The first electronic device 1402 may be charged from any suitable charging technique.

As shown in FIG. 14A, in some embodiments, the electronic devices 1402, 1404 may be stacked or otherwise placed in contact with one another to effectuate the transfer of power from the first device 1402 to the second device 1404. As shown in FIG. 14B, the first device 1402 may transfer power to the second device 1304 using far-field power transfer techniques.

Electronic devices 1402, 1404 may be any electronic device comprising near-field and/or far-field antennas capable of performing the various processes and tasks described herein. For instance, the first device 1402 and the second device 1404 may comprise antennas and circuitry configured to generate, transmit and/or receive RF energy using RF signals. In FIGS. 14A and 14B, the first device 1402 and the second device 1404 are shown as cellular phones. However, this should be not considered to be limiting upon possible electronic devices 1402, 1404. Non-limiting examples of possible electronic devices 1402, 1404 may include tablets, laptops, cell phones, PDAs, smart watches, fitness devices, headsets, or any other device capable of being recharged or operated utilizing the principles described herein.

An antenna of a first electronic device 1402 may generate one or more RF energy signals for wireless power transmission. The one or more RF energy signals may be received by the second device 1404 when an appropriately tuned antenna of the second device 1404 is positioned within a near-field distance (e.g., less than approximately 10 mm) from antenna of the first electronic device 1402. The appropriately tuned antenna of the second device 1404 may thus cause the RF signals to be emitted through the first electronic device 1402 to the antenna of the second device 1404. The received RF energy signals are then converted to a power signal by a power conversion circuit (e.g., rectifier circuit) for providing power to or charging a battery of the second device 1404. In the exemplary embodiments, the total power output by the first electronic device 1402 is less than or equal to 1 Watt to conform to Federal Communications Commission (FCC) regulations part 15 (low-power, non-licensed transmitters).

As shown in FIG. 14A, in some embodiments, the first device 1402 may comprise components for a near field RF charging surface allowing RF energy signals to be trapped beneath a metamaterial surface layer of the first device 1402 until an appropriately tuned antenna of a second device 1404 causes the RF energy to be leaked into the antenna of the second device 1404.

Additionally or alternatively, as shown in FIG. 14B, in some implementations, the first device 1402 may be configured to function as a far-field proximity transmitter comprising an array of one or more antennas configured to transmit one or more power waves to an antenna of the second electronic device 1404.

In some embodiments, the first device 1402 may include a communications component (not shown) to effectuate wireless and/or wired communications to and from other devices, such as the second device 1404. In some cases, a communications component may be an embedded component of the first device 1402; and, in some cases, the communications component may be attached to the first device 1402 through any wired or wireless communications medium. The communications component may comprise electromechanical components (e.g., processor, antenna) that allow the communications component to communicate communications signals containing various types of data and messages with other devices, such as the second device 1404. These communications signals may represent a distinct channel for hosting communications where data may be communicated using any number of wired or wireless protocols and associated hardware and software technology. The communications component may operate based on any number of communication protocols, such as Bluetooth®, Wireless Fidelity (Wi-Fi), Near-Field Communications (NFC), ZigBee, and others. However, it should be appreciated that the communication component is not limited to radio-frequency based technologies, but may include radar, infrared, and sound devices for sonic triangulation of other devices, like the second device 1404.

In operation, the communications component of the first device 1402 may receive communications signals from the second mobile device 1404, where the communications signals contain data that includes a request to receive power from the first device 1402. Additionally or alternatively, the first electronic device 1402 may receive one or more wireless broadcasted messages from the second device 1404, thereby allowing the first electronic device 1302 to detect the presence of the second electronic device 1404 and begin sending power to the second electronic device 1404, or to begin flooding a substrate or cavity layer with RF energy. Such request messages may also include data related to the type of device, battery details of the device, such as battery type and present battery charge, and present location of the device. In some implementations, the first electronic device 1402 may use the data contained within the messages to determine various operational parameters for transmitting or otherwise transferring RF energy to the second device 1404, which the second device 1404 may capture and convert the RF energy into useable alternating current (AC) or direct current (DC) electricity.

For example, when the first device 1402 functions as a near-field charging surface, the first device 1402 may be configured to send power (e.g., engage, turn on, wake up) to a near-field charging surface within the first device 1402 when the communications component of the first electronic device 1402 receives a communications signal having a threshold signal strength indicating that the second device 1404 is within a threshold distance.

As another example, where the first device 1402 functions as a far-field proximity transmitter, the first device 1402 may use the communications signal receive data from the second device 1404 that may be used by the first device 1402 to identify the location of second device 1404 and to determine whether the second electronic device 1404 is within a threshold distance from the first device 1404.

Similarly, a communications component of the second device 1404 may use a communications signal to communicate data that may be used to, for example, send or otherwise broadcast a message to the first device 1402 requesting the first device 1402 to transfer power; the messages may also include, for example, battery power information, data indicating present location, data information about the user of the second device 1404, information about the second device 1404 to be charged, indicate the effectiveness of the power being received, and a request to stop sending the power, as well as other types of useful data. Non-limiting examples of the various types of information that may be included in communications signals may also include a beacon message, a device identifier (device ID) for first device 1402, a user identifier (user ID) for the first device 1402, the battery level for the second device 1404, the second device 1404 location, and other such information.

In some cases, when the second device 1404 enters a near-field distance of the first device 1402 in which the RF energy can be leaked and emitted from the first device 1402 into the second device 1404, the devices may establish a communications channel according to the wireless or wired communications protocol (e.g. Bluetooth®) employed by the respective communications components of the respective devices 1402, 1404. In some cases, the second device 1404 may establish a communication channel with the first device 1402 upon entering the effective communications distance of the first device 1402 of the wired or wireless communications protocols employed by the communications components. A near-field distance may be defined as a minimum distance between a transmitter-side device (e.g., first electronic device 1402) and a receiver-side device (e.g., second electronic device 1404) that would cause the transmitter-side device to leak and transfer trapped RF wave signals into the appropriately tuned receiver-side device. This near-field distance may range from direct contact to about 10 millimeters. In some cases, a proximate far-field distance may be the minimum distance between a transmitter-side device to transmit one or more power waves to a receiver-side device, which may range up to about 12 inches. In an alternative embodiment, any far-field distance can be used.

The antennas of the second device 1404 may capture energy from the RF signals leaked or emitted from the first device 1402 or from the power waves transmitted from the first device 1402. After RF signals are received from the power waves or from the leakage, from the first device 1302, circuitry and other components (e.g., integrated circuits, amplifiers, rectifiers, voltage conditioner) of both the first and second devices 1402, 1404 may then convert the energy of the RF signals (e.g., radio frequency electromagnetic radiation) to electrical energy (i.e., electricity), which may be stored into a battery or may power the respective electronic device 1402, 1404. In some cases, for example, a rectifier of a second device 1404 may convert the electrical energy from AC to DC form, usable by the second device 1404. Other types of conditioning may be applied as well, in addition or as an alternative to, conversion from AC to DC. For example, a voltage conditioning circuit, such as a voltage regulator, may increase or decrease the voltage of the electrical energy as required by the second device 1404.

FIG. 15 show components of a wireless charging system 1500 among a plurality of electronic devices 1502, 1504, according to exemplary embodiments. For ease of explanation, FIG. 15 show wireless power transfer among two devices 1502, 1504. However, it will be appreciated by a person having ordinary skill in the art that wireless power transfer as described herein may occur among two or more electronic devices. In the exemplary embodiment, a first electronic device 1502 may receive power from a charging case 1506 through near-field charging techniques, and may then, in turn, provide power to a second electronic device 1504. The charging case 1506 may include a battery that is used to transfer power to the first electronic device 1502 and/or the second electronic device 1504.

As shown in FIG. 15, in some embodiments, the electronic devices 1502, 1504 may be stacked or otherwise placed in contact with one another to effectuate the transfer of power from the charging case 1506 to the second device 1504. The first device 1502 may receive power from the charging case 1506 using near-field power transfer techniques, and then the first device 1502 may transfer power to the second device 1504 using far-field power transfer techniques. The first device 1502 doesn't transmit its own power to the second device 1504 but transmits the power received from the charging case 1506 to the second device 1504. The second device 1504 may also be able to receive the power directly from the charging case 1506 using far-field power transfer techniques.

Electronic devices 1502, 1504 may be any electronic device comprising near-field and/or far-field antennas capable of performing the various processes and tasks described herein. For instance, the first device 1502 and the second device 1504 may comprise antennas and circuitry configured to generate, transmit and/or receive RF energy using RF signals. In FIG. 15, the first device 1502 and the second device 1504 are shown as cellular phones. However, this should be not considered to be limiting upon possible electronic devices 1502, 1504. Non-limiting examples of possible electronic devices 1502, 1504 may include tablets, laptops, cell phones, PDAs, smart watches, fitness devices, headsets, or any other device capable of being recharged or operated utilizing the principles described herein.

A charging case 1506 such as a battery may store RF energy signals for wireless power transmission. The stored RF energy may be leaked through the top surface and received by the first device 1502 when an appropriately tuned antenna of the first device 1502 is positioned within a near-field distance (e.g., less than approximately 10 mm) from the charging case 1502. The appropriately tuned antenna of the first device 1502 may thus cause the RF signals stored within the charging case 1506 to be leaked or emitted through the charging case 1506 to the antenna of the first device 1502. The first device 1502 is configured to function as a far-field proximity transmitter comprising an array of one or more antennas configured to transmit the received RF signals to an antenna of the second electronic device 1504. The RF energy signals received by the second electronic device 1504 are then converted to a power signal by a power conversion circuit (e.g., rectifier circuit) for providing power to or charging a battery of the second device 1504. In the exemplary embodiments shown in FIG. 15, the charging case 1502 may be shown as a box-shaped battery device, but it should be understood that the charging case 1502 may have any size, form-factor, configuration, and/or shape. In some embodiments, the total power output by the charging case 1502 is less than or equal to 1 Watt to conform to Federal Communications Commission (FCC) regulations part 15 (low-power, non-licensed transmitters).

In some embodiments, the second device 1504 may include a communications component (not shown) to effectuate wireless and/or wired communications to and from other devices, such as the charging case 1502 and/or the first device 1502. In some cases, a communications component may be an embedded component of the second device 1504; and, in some cases, the communications component may be attached to the first device 1504 through any wired or wireless communications medium.

The communications component of the second device 1504 may use a communications signal to communicate data that may be used to, for example, send or otherwise broadcast a message to the first device 1502 requesting the first device 1502 to transfer power; the messages may also include, for example, battery power information, data indicating present location, data information about the user of the second device 1504, information about the second device 1504 to be charged, indicate the effectiveness of the power being received, and a request to stop sending the power, as well as other types of useful data.

The first device 1502 would then cause the charging case 1502 (transmitter-side device) to leak and transfer RF wave signals into the appropriately tuned first device 1502 (receiver-side device). The antennas of the second device 1504 may then capture energy from the RF signals leaked or emitted from the first device 1502 or from the power waves transmitted from the first device 1502. After RF signals are received from the power waves or from the leakage, from either the charging case 1502 or the first device 1502, circuitry and other components (e.g., integrated circuits, amplifiers, rectifiers, voltage conditioner) of the second device 1504 may then convert the energy of the RF signals (e.g., radio frequency electromagnetic radiation) to electrical energy (i.e., electricity), which may be stored into a battery or may power the electronic device 1504. The first device 1502 is configured to not transmit its own power to the second device 1504 but to transfer the power received from the charging case 1506 to the second device 1504. In some cases, for example, a rectifier of a second device 1504 may convert the electrical energy from AC to DC form, usable by the second device 1504. Other types of conditioning may be applied as well, in addition or as an alternative to, conversion from AC to DC. For example, a voltage conditioning circuit, such as a voltage regulator, may increase or decrease the voltage of the electrical energy as required by the second device 1504.

FIG. 16 is a flow diagram illustrating operations of the wireless power transfer among a plurality of devices, in accordance with an embodiment the present disclosure.

At step 1602, a second device enters a near-field distance of a first device. In an embodiment, a user of second device may manually place the second device in a near-field distance from the first device. The near-field distance may be less than about 10 mm. The first device and the second device may include circuitry configured to generate, transmit and receive RF signals. The circuitry of the first device and the second device may include a plurality of unit cells, and the plurality of unit cells are configured to receive an RF signal.

At step 1604, a communication channel is established between the second and the first devices. The first and the second device may include a communication component via which a communication channel may be established to transmit data among each other. The communications component may operate based on any number of communication protocols, such as Bluetooth®, Wireless Fidelity (Wi-Fi), Near-Field Communications (NFC), ZigBee, and others.

In one embodiment, the communication channel may be established between the first and the second devices prior to the second device entering the near-field of the first device. In another embodiment, the communication channel may be established between the first and the second devices after the second device enters the near-field of the first device.

At step 1606, the second device then sends a request to receive power to the first device via the communication channel for charging its battery. In another embodiment, a user of the second device via a user interface of the second device sends a request to receive power to the first device. Along with the request, the second device may include additional data including but not limited to user of the second device, details of the second device, battery charge of the second device, or current location of the second device. Upon receiving a charging request, the first device may accept or decline the request. In another embodiment, a user of the first device may accept or decline the request via the user interface of the first device. The response to the request may be received on the user interface of the second device.

At step 1608, the second device may charge a battery using received RF signals from the first device. After accepting the request of the second device, the first device may determine the location of the second device. Once the location of the second device is determined, then the first device may transmit RF signals to the second device, which may be captured by antennas and/or circuitry of the second device to charge the battery of the second device.

In some embodiments the initiation of the power transfer from the first device to the second device is done by a user of the devices on a user interface of the first and/or second devices. The user may select when to start, stop wireless charging from one device to the other, and the user may further select which device becomes the transmitter and which device becomes the receiver. Furthermore, the user may select termination of the power transfer by selecting a target time, target power level, etc.

The antennas of the second device may harvest energy from RF signals, which may be formed from the resulting accumulation of the RF signals at its location. After the RF signals are received and/or energy is gathered from a pocket of energy, circuitry (e.g., integrated circuits, amplifiers, rectifiers, voltage conditioner) of the second device may then convert the energy of the RF signals (e.g., radio frequency electromagnetic radiation) to electrical energy (i.e., electricity), which may be stored into a battery of the second device.

In one embodiment, the circuitry of the first device includes a plurality of unit cells configured to receive the RF signal and cause an RF energy signal to be present for charging the battery of the second device in response to antenna of the second device being positioned in the near-field distance of at least one of the unit cells. In another embodiment, the circuitry of the second device includes a plurality of unit cells configured to receive the RF signal and cause an RF energy signal to be present for charging a battery of the first device in response to an antenna of the first device being positioned in the near-field distance of at least one of the unit cells.

The foregoing method descriptions and flow diagrams are provided merely as illustrative examples and are not intended to require or imply that the steps of the various embodiments must be performed in the order presented. The steps in the foregoing embodiments may be performed in any order. Words such as “then,” “next,” etc., are not intended to limit the order of the steps; these words are simply used to guide the reader through the description of the methods. Although process flow diagrams may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be rearranged. A process may correspond to a method, a function, a procedure, a subroutine, a subprogram, etc. When a process corresponds to a function, its termination may correspond to a return of the function to the calling function or the main function.

The various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

Embodiments implemented in computer software may be implemented in software, firmware, middleware, microcode, hardware description languages, or the like, or any combination thereof. A code segment or machine-executable instructions may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and/or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted via any suitable means including memory sharing, message passing, token passing, network transmission, etc.

The actual software code or specialized control hardware used to implement these systems and methods is not limiting of the invention. Thus, the operation and behavior of the systems and methods were described without reference to the specific software code being understood that software and control hardware can be designed to implement the systems and methods based on the description herein.

When implemented in software, the functions may be stored as one or more instructions or code on a non-transitory computer-readable or processor-readable storage medium. The steps of a method or algorithm disclosed herein may be embodied in a processor-executable software module which may reside on a computer-readable or processor-readable storage medium. A non-transitory computer-readable or processor-readable media includes both computer storage media and tangible storage media that facilitate transfer of a computer program from one place to another. A non-transitory, processor-readable storage media may be any available media that may be accessed by a computer. By way of example, and not limitation, such non-transitory, processor-readable media may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other tangible storage medium that may be used to store desired program code in the form of instructions or data structures and that may be accessed by a computer or processor. Disk and disc, as used herein, include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media. Additionally, the operations of a method or algorithm may reside as one or any combination or set of codes and/or instructions on a non-transitory, processor-readable medium and/or computer-readable medium, which may be incorporated into a computer program product.

The preceding description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the following claims and the principles and novel features disclosed herein.

While various aspects and embodiments have been disclosed, other aspects and embodiments are contemplated. The various aspects and embodiments disclosed are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims. 

What is claimed is:
 1. A first wireless-power receiver, comprising: a first antenna configured to transmit first near-field radio frequency (RF) energy to a second wireless-power receiver; a second antenna configured to receive second near-field RF energy from the second wireless-power receiver or from a wireless-power transmitter; and a communications component configured to provide a communication signal including data indicating a location of the first wireless-power receiver, wherein the first wireless-power receiver is configured to: in accordance with a determination that the first wireless-power receiver is in direct contact with a surface of the second wireless-power receiver, transmit the first near-field RF energy, via the first antenna, to the second wireless-power receiver; and in accordance with a determination, based on the data indicating the location of the first wireless-power receiver, that the first wireless-power receiver is within a non-zero threshold distance from the second wireless-power receiver or the wireless-power transmitter, receive the second near-field RF energy, via the second antenna, from the second wireless-power receiver or from the wireless-power transmitter.
 2. The first wireless-power receiver of claim 1, wherein the first wireless-power receiver is configured to transmit the first near-field RF energy, via the first antenna, to the second wireless-power receiver only after receiving a request for wireless power from the second wireless-power receiver.
 3. The first wireless-power receiver of claim 1, wherein first wireless-power receiver is configured to receive the second near-field RF energy, via the second antenna, from the second wireless-power receiver or from the wireless-power transmitter after providing a request for wireless power.
 4. The first wireless-power receiver of claim 1, wherein the non-zero threshold distance is up to 10 mm.
 5. The first wireless-power receiver of claim 1, wherein the first and second antennas are distinct antennas.
 6. The first wireless-power receiver of claim 1, wherein the first wireless-power receiver is configured to determine one or more parameters for the first near-field RF energy based at least in part on data received from the second wireless-power receiver.
 7. The first wireless-power receiver of claim 6, wherein: the data received from the second wireless-power receiver includes battery level information; and the first wireless-power receiver is configured to determine the one or more parameters for the first near-field RF energy based at least in part on the battery level information.
 8. The first wireless-power receiver of claim 1, further comprising: a third antenna configured to transmit far-field RF energy, wherein the first wireless-power receiver is configured to: in accordance with a determination, based on the data indicating the location of the first wireless-power receiver, that the first wireless-power receiver is within a non-zero far-field threshold distance from the second wireless-power receiver or the wireless-power transmitter, receive the far-field RF energy, via the third antenna, from the second wireless-power receiver or from the wireless-power transmitter.
 9. The first wireless-power receiver of claim 8, wherein the non-zero far-field threshold distance is up to 12 inches.
 10. The first wireless-power receiver of claim 1, wherein the first wireless-power receiver is configured to convert the RF energy received from the second wireless-power receiver or the wireless-power transmitter into electrical energy for charging a battery of an electronic device coupled to the wireless-power receiver or for powering the electronic device.
 11. A method of wirelessly transferring power with a first wireless-power receiver, the method comprising: at the first wireless-power receiver comprising a first antenna configured to transmit first near-field radio frequency (RF) energy, a second antenna configured to receive second near-field RF energy, and a communications component: providing a communication signal including data indicating a location of the first wireless-power receiver; in accordance with a determination that the first wireless-power receiver is in direct contact with a surface of the second wireless-power receiver, transmitting the first near-field RF energy, via the first antenna, to a second wireless-power receiver; and in accordance with a determination, based on the data indicating a location of the first wireless-power receiver, that the first wireless-power receiver is within a non-zero threshold distance from the second wireless-power receiver or a wireless-power transmitter, receiving the second near-field RF energy, via the second antenna, from the second wireless-power receiver or from the wireless-power transmitter.
 12. The method of claim 11, wherein the first wireless-power receiver is configured to transmit the first near-field RF energy, via the first antenna, to the second wireless-power receiver only after receiving a request for wireless power from the second wireless-power receiver.
 13. The method of claim 11, wherein first wireless-power receiver is configured to receive the second near-field RF energy, via the second antenna, from the second wireless-power receiver or from the wireless-power transmitter after providing a request for wireless power.
 14. The method of claim 11, wherein the non-zero threshold distance is up to 10 mm.
 15. The method of claim 11, wherein the first and second antennas are distinct antennas.
 16. The method of claim 11, further comprising determining one or more parameters for the first near-field RF energy based at least in part on data received from the second wireless-power receiver.
 17. The method of claim 16, wherein: the data received from the second wireless-power receiver includes battery level information; and the method further comprises determining the one or more parameters for the first near-field RF energy based at least in part on the battery level information.
 18. The method of claim 11, wherein the first wireless-power receiver further comprises a third antenna configured to transmit far-field RF energy; and the method further comprises in accordance with a determination, based on the data indicating the location of the first wireless-power receiver, that the first wireless-power receiver is within a non-zero far-field threshold distance from the second wireless-power receiver or the wireless-power transmitter, receiving the far-field RF energy, via the third antenna, from the second wireless-power receiver or from the wireless-power transmitter.
 19. A non-transitory computer-readable storage medium storing executable instructions that, when executed by one or more processors that are in communication with a first wireless-power receiver, cause the first wireless-power receiver to: provide a communication signal including data indicating a location of the first wireless-power receiver; in accordance with a determination that the first wireless-power receiver is in direct contact with a surface of the second wireless-power receiver, transmit the first near-field RF energy, via the first antenna, to a second wireless-power receiver; and in accordance with a determination, based on the data indicating a location of the first wireless-power receiver, that the first wireless-power receiver is within a non-zero threshold distance from the second wireless-power receiver or a wireless-power transmitter, receive the second near-field RF energy, via the second antenna, from the second wireless-power receiver or from the wireless-power transmitter.
 20. The non-transitory computer-readable storage medium of claim 19, wherein the first wireless-power receiver is configured to transmit the first near-field RF energy, via the first antenna, to the second wireless-power receiver only after receiving a request for wireless power from the second wireless-power receiver. 